The present invention relates to an apparatus for hand polishing various style fiber optic connectors. Specifically, the polishing apparatus is disc shaped and is configured to receive the ferrule portion of SC, SC Duplex, ESCON, ST, FC, MP, FDDI, or other planar multifiber connectors.
Fiber optic cables allow information signals to be transmitted from one point to another using light signals carried on a single glass fiber. During the installation of fiber optic systems, it is often necessary perform field splices to join separate fiber optic cables together so that light signals can be transferred over distances greater than the length of a single cable. Splicing fiber optic cables requires precise alignment of the individual fibers being joined in order to provide a noninterrupted fiber path for the light signals to travel through. The joined fibers must be both axially and radially aligned to ensure that the light signal is transferred from one fiber to the next.
Precision fiber optic connectors are provided to achieve proper alignment between independent optical fibers within a fiber optic splice. Such connectors include alignment ferrules made of ceramic, plastic, or some other rigid material. Each ferrule is formed with at least one internal channel for receiving an optical fiber, depending on the style of connector. A fiber optic cable is stripped to a predetermined length so that the signal carrying fiber strand or multiple strands are exposed. Epoxy is then inserted into the internal channels of the ferrule. Individual fiber strands are then inserted into the individual channels until they extend beyond the front face of the ferrule. The Epoxy is then allowed to cure so as to firmly secure the fiber strand or strands within the ferrule. Once the epoxy has set, the fiber strands are cleaved as near to the epoxy as possible using a sharp blade. The face of the ferrule is then polished to provide a smooth flat surface which can be placed in direct face to face abutment against a similarly prepared ferrule. When making the connection between the two cables, the shape of the two ferrules and their associated connector hardware ensure that the fibers contained within ferrules will be axially aligned. Polishing the face of the ferrules ensures that the optical fiber or fibers within the ferrule will have smooth flat surfaces perpendicular to the axis of the fiber. Thus, when the faces of the ferrules are abutted up against one another, the surfaces of the adjacent fibers will be flush with one another such that throughout the length of the ferrules the two strands are held in linear alignment, thereby allowing light signals to pass from one strand to the next without interruption.
From the above description, it should be clear that polishing the face of the connector ferrules is a key step in performing a successful fiber optic splice. In many cases, splices are being made in the field as the fiber optic cables are being installed rather than in the factory where the connectors are made. Under field conditions it is generally necessary to polish the ferrules by hand. This is most readily accomplished by inserting the ferrule into a polishing disc specifically designed for this task, and rubbing the disc over various grades of polishing film.
Polishing discs are known in the art. Such disks are generally formed having a planar lower polishing surface and having a ferrule receiving hole, or holes, extending through the disc perpendicular to the lower polishing surface. The ferrule receiving hole or holes are configured to receive the ferrules of a particular fiber optic connector style. To polish a single ferrule, the ferrule is inserted into a ferrule receiving hole until the end of the ferrule protrudes slightly from the lower polishing surface of the disc. A piece of polishing paper is then laid out on a flat surface and the polishing disc placed over the polishing paper, with the lower polishing surface of the disc engaging the polishing paper. The polishing disc is then rubbed vigorously over the polishing paper. The lower polishing surface of the polishing disc acts as a reference plane, and the rough surface of the ferrule face extending beyond the reference plane will be worn away by the action of the polishing paper. This process is usually carried out a number of times using a finer and finer grade polishing paper with each iteration. The result is a clean, smooth, and flat face portion of the fiber strand contained within the ferrule. The process can also be applied to multiple ferrule connectors, provided that properly spaced ferrule receiving holes are provided.
Differing fiber optic applications will often have differing connector requirements. In some applications where large amounts of data to be must be transferred, more than one fiber will be necessary to accommodate all of the data flow. For example, many applications require separate transmit and receive lines for bi-directional communication between devices. Other applications may simply require a large number of fibers in order to transfer massive amounts of data. Yet another application may require only a single fiber strand. To accommodate this wide variety of fiber optic applications, a wide variety of fiber optic connector styles has developed. SC, ST, and FC style connectors are all single fiber connectors. Each of these connectors has a single ferrule encasing a single fiber, the differences between these styles lie in the manner in which the outer casings of the connectors are connected. The SC Duplex connector is basically two single SC connectors clipped together in a predefined manner, and having a predefined spacing between the two ferrules for accommodating bi-directional data transfer. Thus, splicing utilizing an SC Duplex connector requires the polishing of two conjoined ferrules. Similarly, the ESCON and FDDI connectors are two ferrule connectors having a single rigid connector body. The two ferrules, each containing a single fiber, extend from the connector body with a wider standard spacing than the SC Duplex standard spacing. Finally, the MP connector is a single ferrule connector capable of holding multiple fibers (as many as twelve fibers) within the single ferrule. While the ferrules of the SC, ST, FC, and ESCON are all round, the MP ferrule and other planar multifiber connector ferrules are generally rectangular in shape, having beveled lateral sides.
Until now, with the exception of the single fiber connectors such as the SC, ST and FC, a separate polishing disc has been required to polish each style connector in order to accommodate the various arrangements of the connector ferrules. Thus, the wide variety of connector styles employed by fiber optic systems can be an inconvenience for those charged with the task of installing them. Not only must the installation technician carry a wide range of connectors to meet the varied requirements of an installation, but a wide range of polishing discs must be carried as well, in order to polish whichever style connector happens to be required for a given splice.
Another problem with existing polishing discs is that they are subject to wear. The polishing paper used to polish the ferrules is naturally abrasive. The constant rubbing of the disc over abrasive polishing paper wears down the lower polishing surface of the disc. This can cause the polishing surface to become uneven. An uneven polishing surface can cause an uneven finish to be imparted to the ferrule which can adversely affect the quality of the splice achieved by the connector.
Another shortcoming of existing polishing discs is that they are generally configured to polish a single connector at a time. It is possible to form multiple ferrule receiving holes in the disc for polishing more than one connector ferrule at a time, however, this often leads to unsatisfactory results. When more than one independent ferrule is to be polished, it is difficult to exert the same amount of downward pressure on each connector to ensure that the face of each ferrule is being adequately polished. Again this can result in an inferior finish being imparted to the face of the ferrules, with the concomitant degradation in the quality of the splice. Thus, the time saving advantage of polishing more than one connector at a time is lost with existing polishing discs.
To overcome the shortcomings of existing fiber optic ferrule polishing discs, it is necessary to develop a universal ferrule polishing apparatus capable of use with a wide variety of fiber optic connector styles. Such an apparatus should have multiple ferrule receiving holes arranged in a pattern such that the ferrules of variety of single and multi-fiber connectors can be inserted into the apparatus, achieving a degree of universality between connector styles. The improved apparatus should also provide means for protecting the lower polishing surface from wear. Preferably the protecting means would be in the form of hardened surfaces (harder than the polishing surface of the improved polishing apparatus) which extend slightly beyond the plane of the polishing surface. Finally, the improved apparatus should be configured to receive tooling adapted to exert uniform downward pressure against multiple connector ferrules inserted into the ferrule receiving holes.